By Sarah N. Lynch WASHINGTON (Reuters) – Rod Rosenstein, the U.S. official overseeing an investigation of ties between President Donald Trump’s election team and Russia, warned a group of conservative Republicans on Tuesday that his department would not be “extorted” and criticized them for leaking a draft resolution calling for his impeachment. Rosenstein, U.S. Deputy Attorney General, has been under fire since last May when he appointed Special Counsel Robert Mueller to investigate Russia’s suspected interference in the 2016 election and possible collusion by the Trump campaign.